The present invention relates to dental handpiece coupling assemblies for drivingly connecting gears so as to rotate a dental tool in a dental head. It is desirable to have a dental handpiece which allows interchange of different dental tools according to the type of dental work necessary. One way to change dental tools is to simply remove the tool from the dental head and replace it with another desired tool. However, the small size of dental tools makes them difficult to handle. It is therefore desirable to interchange one dental head with another, so that the larger heads can be disconnected and re-connected to the handpiece, rather than having to handle the smaller individual tools themselves.
When two new gears are initially mated in a dental handpiece, they can be aligned so as to mesh properly for driving rotation. After a period of time, those first and second mating gears become worn and mishapened through use, so that their shape is somewhat distorted from their original shape. The alignment of the two gears with their surrounding elements can also be altered during use. Because the distortion and misalignment of the two gears occurs while they are mated, the distortions and misalignment are mirrored in the two gears, so that they remain in proper mesh and alignment with each other for driving engagement.
Thus, when one of these first or second mated gears is replaced by a third gear, the third gear may not mesh well with, or be aligned with, the other mating gear, because of the distortion that has been created between the two gears during their operation. This is true although the three gears were probably nearly identical after they were manufactured and before they were used. Therefore, it is desirable to have an interchange system whereby there is no substitution of either the driven gear or drive gear.
Another problem with meshing and unmeshing gears is that if the drive gear remains running when the driven gear is brought into mesh with it, the gear teeth may tear into each other and ruin the gears.
The present invention alleviates such problems. It provides a first coupling assembly mounted within the shoulder sleeve of a dental handpiece, so that it rotates therein. The first coupling assembly comprises a gear such as a bevel gear, which is driven by another gear that is driven from the power source. The first coupling assembly has a drive shaft extending from its gear into a coupling hand. In the preferred embodiment, the coupling hand comprises a pair of tongues mounted opposite one another with slots formed between the tongues.
The invention further comprises a second coupling assembly which can be similar to the first. The second assembly has a hand having a pair of tongues with slots formed therebetween. The second coupling assembly likewise has a drive shaft extending from its hand to connection with a gear. The second assembly can be mounted to the dental head by a throat sleeve so that the second assembly's gear is drivingly connected to a driven gear mounted within the head for purposes of driving a dental tool. The coupling assemblies thus allow the head to be attached and detached from the shoulder. In the preferred embodiment, the tongues of the first assembly fit in the slots between the tongues of the first coupling assembly, so that straight side walls of the tongues of both coupling assemblies fit flush with each other for driving connection.
In the preferred embodiment the tongues have anterior ends shaped to guide the tongues into driving engagement as they are moved towards one another. These ends can be slanted to come to a point. When the head is mounted to the shoulder, and the tongues of the second coupling assembly are moved towards the tongues of the first coupling assembly, the slanted ends engage and direct the tongues towards the slots formed between the side walls of the tongues.
Thus, the head with its second coupling assembly can be pulled away from the shoulder sleeve with its first coupling assembly to disengage the coupling assemblies. Another like head with a different dental tool mounted thereto, can then be substituted for the first head, and have its corresponding second coupling assembly moved back into the shoulder sleeve bore until the hand of the second coupling assembly interlocks with the hand of the first coupling assembly for driving engagement.
With the present invention there is thus provided a coupling assembly arrangement whereby mated gears remain with their mated gears during interchange of components. There is thus elimination of the situation where a gear is caused to mate with a foreign gear resulting in improper meshing and misalignment of the gears. This reduces the opportunity for malfunctioning. Thus, the special distortions and alignment of the gears formed as a result of their operation are not caused to be suddenly interacted with a foreign non-conforming gear shape.
Because the gears are not directly involved in the coupling change, during the installation and disconnection there is no moving of gear teeth into mesh or out of mesh, even if the installation or disconnection is performed while the dental tool is being operated. This eliminates the possibility of the gears tearing into each other during such installation and disconnection.
A further feature is that the first assembly can be mounted entirely within the walls of the shoulder so as to be recessed therein. There is thus no problem with snagging occurring if the dental power motor is allowed to run during the interchange process. The invention also provides bearing sleeves which properly mount the coupling assemblies for their operation.